An investigation into the bulk nature of some transistion metal carbonyls
An investigation into the bulk nature of some transistion metal carbonyls
Investigations into the structure of ruthenium and osmium carbonyl clusters have been performed using the technique of vibrational spectroscopy. A series of clusters ranging in nuclearity from 3 to 20 has been synthesised and the solid state IR and, where possible, Raman spectra acquired. Fully symmetrised vibrational simulations over the range 0 to ca. 2000 cm-1 have been performed using the SOTONVIB suite of programs and a model derived from the structure of the original cluster, and the spectrum generated refined using experimental IR and Raman frequencies. For the clusters Ru3(CO)12, Os3(CO)12, H4Os4(CO)12 and Ru5C(CO)15 the average discrepancy between the calculated and the observed frequencies after 50 cycles of refinement is of the order of 25 to 50 cm-1: the regions of the vibrational spectrum in which vibrations occur match well with those observed experimentally. For larger clusters, refinement has been less successful: this is primarily due to the difficulty in obtaining a satisfactory set of Raman data. Simulated spectra for the clusters H2Ru6(CO)18, [Os6(CO)18]2-, [Ru10C(CO)24]2-, [Os10C(CO)24]2-, and [Os20(CO)40]2- have been refined by hand using solution v(CO) IR data to give average errors of the order of 5 to 10 cm-1 for this region. A comparison of observed and calculated intensities for the v(MC) vibrations which have been observed at ca. 580 cm-1 in the spectra of all these clusters shows a relative increase in intensity for the largest clusters which, by resource to the surface selection rule, is proposed to be indicative of bulk nature. On the basis of this work it may be concluded that [Os20(CO)40]2- may be showing a certain degree of bulk nature, a conclusion which agrees with theoretical predictions.
Large single crystals of Rh2(CO)4Cl2, Rh(CO)2[hfac], and Rh(CO)2[acac] have been grown and polarised IR and Raman spectra acquired.
University of Southampton
1994
Larcombe, Helen Eileen
(1994)
An investigation into the bulk nature of some transistion metal carbonyls.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Investigations into the structure of ruthenium and osmium carbonyl clusters have been performed using the technique of vibrational spectroscopy. A series of clusters ranging in nuclearity from 3 to 20 has been synthesised and the solid state IR and, where possible, Raman spectra acquired. Fully symmetrised vibrational simulations over the range 0 to ca. 2000 cm-1 have been performed using the SOTONVIB suite of programs and a model derived from the structure of the original cluster, and the spectrum generated refined using experimental IR and Raman frequencies. For the clusters Ru3(CO)12, Os3(CO)12, H4Os4(CO)12 and Ru5C(CO)15 the average discrepancy between the calculated and the observed frequencies after 50 cycles of refinement is of the order of 25 to 50 cm-1: the regions of the vibrational spectrum in which vibrations occur match well with those observed experimentally. For larger clusters, refinement has been less successful: this is primarily due to the difficulty in obtaining a satisfactory set of Raman data. Simulated spectra for the clusters H2Ru6(CO)18, [Os6(CO)18]2-, [Ru10C(CO)24]2-, [Os10C(CO)24]2-, and [Os20(CO)40]2- have been refined by hand using solution v(CO) IR data to give average errors of the order of 5 to 10 cm-1 for this region. A comparison of observed and calculated intensities for the v(MC) vibrations which have been observed at ca. 580 cm-1 in the spectra of all these clusters shows a relative increase in intensity for the largest clusters which, by resource to the surface selection rule, is proposed to be indicative of bulk nature. On the basis of this work it may be concluded that [Os20(CO)40]2- may be showing a certain degree of bulk nature, a conclusion which agrees with theoretical predictions.
Large single crystals of Rh2(CO)4Cl2, Rh(CO)2[hfac], and Rh(CO)2[acac] have been grown and polarised IR and Raman spectra acquired.
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Published date: 1994
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Local EPrints ID: 462810
URI: http://eprints.soton.ac.uk/id/eprint/462810
PURE UUID: 597b9b7e-282c-4eee-829e-2b8ef0e6a04f
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Date deposited: 04 Jul 2022 20:08
Last modified: 04 Jul 2022 20:08
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Author:
Helen Eileen Larcombe
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